The impedance measurements can be done with a direct connection to the analyzing hardware or with an external amplifier and a sensing resistor both in constant current or constant voltage configurations.
Using an Audiomatica QCBox Amplifier, its current sensing output is used to permit simultaneous frequency response and impedance measurement.
The evaluation of speaker parameters may use a single-pass, non-invasive, laser displacement measurement or the classical added-mass or known-volume methods with least square error routines.